E1) As said in an article by journalist Raymond Cushing, and as forwarded by The American Medical Marijuana Association, in 1974 researchers at the Medical College of Virginia, who were funded by the National Institute of Health, learned that THC shrank or destroyed brain tumors in test mice and the results were recently repeated by further research in 2000. [1,2]

E2) Marijuana components, including THC, have been found to inhibit the growth of the most common, and aggressive form of brain tumor, a glioblastoma, according to a study published in a 2010 issue of Molecular Cancer Therapeutics, under the American Association for Cancer Research, which was repeated by Patients for Medical Cannabis.[3,4]

E3) According to a 2009 study recorded in The Journal for Clinical Investigation, cannabinoid action induces autophagy-mediated cell death through stimulation of ER stress in human glioma cells. [5]

E4) As reported by Science Daily and the Huffington Post, in 2009 Guillermo Velasco and colleagues, at Complutense University, Spain, have provided evidence that suggests that cannabinoids such as the main active component of marijuana (THC) have anticancer effects on human brain cancer cells. [6,7]

I wish to thank my opponent for opening their case, and their use of such reliable sources by well-respected scientists. My opponent cited three studies conducted under controlled conditions (in chronological order):

Virginia studyMadrid studyCalifornia study

In order to win this debate, I must explain why the science behind these studies is bad. Before you read both my opponent's articles and my critique, please make sure you are familiar with the concept of confirmation bias. You can read more about this at http://en.wikipedia.org....

The Virginia study, for which the supplementary material has been lost (so the study cannot be verified or confirmed), purports to have tested a few dozen mice and found those given THC had their lives prolonged by about a third. There are 5 major problems with this study. First, the lack of supplementary materials means the raw data cannot be examined. Looking at an abstract report does not give a good statistical overview. Second, the sample size was reasonably small. Third, the sample was not a human sample (I assume this debate is about human cancerous cells, which behave differently) and therefore irrelevant. Fourth, injecting some cancerous mice with THC is an example of confirmation bias - the researchers were checking whether there was any benefit to using THC. You wouldn't do an experiment like that unless you thought there was (people don't just go around testing every single substance). Fifth, the study did not investigate tumor size (which is the focus of this debate) but survival time.

In the Madrid study, mice were given human tumors (that's better!) and some were given THC. In those with THC, some were found to have smaller tumors than others. Researchers isolated the process responsible for this as being autophagy. They also tested two human brain cancer patients and found a few dead cancer cells (and also dead patients). First, note the ridiculously small sample size. You can't test two people and a handful of mice and then conclude that THC inhibits cancerous cells. Even the study's authors admit further research is needed before causation can be established. Second, still on causation, the process of autophagy was isolated in a test tube. Based on this, the scientists looked for signs of autophagy. This is the most extreme case of confirmation bias I have ever seen in a medical journal.

Lastly, the California study. This showed that cannabidiol can enhance the activity of THC. The study therefore presupposed that THC cures cancer.

It is worth noting that none of these studies show any survival benefit. 40% of American cancer patients use marijuana or other alternative therapies, and the numbers are increasing - but the rate of cancer survival hasn't really changed. To win this debate, according to my opponent's own rubric, they need to show not only that THC reduces tumor size, but also that it is an effective treatment. The word "effective" suggests it must be of a standard of effectiveness set by convention. None of these studies even assert, let alone prove, that the standard is anywhere near that of conventional methods at reducing the size of tumors.

I therefore think the evidence is not yet clear and more research is needed before we can conclude THC is an effective treatment for treating cancerous tumors. I look forward to hearing my opponent's evidence to the contrary.

Props to Larz for the articulateness of his explanations. I will now defend the studies I presented and address the specific points made against them.

P1) Confirmation Bias

a. Virginia StudyCon said "Injecting some cancerous mice with THC is an example of confirmation bias - the researchers were checking whether there was any benefit to using THC."There are two logical fallacies here. First, one can not conclude confirmation bias has been performed in an experiment solely off the nature of what is being tested(i.e. whether THC is beneficial). Secondly, it is fallacious to conclude what the motivations of the researches are based on the nature of what is being tested.Ergo, Con has not substantiated his claim that the Virginia study is an example of confirmation bias.

b. Madrid StudyCon said "The process of autophagy was isolated in a test tube. Based on this, the scientists looked for signs of autophagy. This is the most extreme case of confirmation bias I have ever seen in a medical journal."The same two logical fallacies apply to this claim. Ergo, Con has not substantiated his claim that the Madrid study is an example of confirmation bias.

c. California StudyCon said "This showed that cannabidiol can enhance the activity of THC. The study therefore presupposed that THC cures cancer."This is both false and non sequitur. The study states that both compounds were tested individually and that they were found to have a more effective result when combined.Ergo, Con has not substantiated his claim that the California study is an example of confirmation bias.

P2) Mice vs. Human test subjects

a. Virginia studyI cannot confirm that human cancer cells were used since I don't have the study but I can conclude that this is very likely considering the purpose for using mice in cancer research is because human cancer cells can be grafted to them without rejection. [1] As Con pointed out, this was the case in the Madrid study.

b. California StudyHumans were used.

c. First-hand accountCon did not address the first-hand account of humans being effectively treated for cancerous tumors with marijuana, which I presented with video.

P3) Sample SizeI assert that fault in sample size can be out-ruled due to the number of studies that repeat the same results and the degree to which the results made themselves clear.

CONCLUSION

It is a reasonable conclusion that the studies I have presented have passed the scientific method, affirming the resolution, and Con has not substantiated otherwise.

I'd like to thank my opponent for going the extra mile to get his case written up, despite having to go to a camp for a few days. In concluding his case, pro generalized three broad points of clash:

Confirmation biasUse of MiceSample size

He also pointed out that I did not respond to his first-hand account. I have two responses. First, my opponent did not respond to many of my points - for example, that the Virginia study did not investigate tumor size and that none of the studies show "effectiveness". More importantly, however, I did respond by presenting more credible conflicting evidence. I told you 40% of American cancer patients are now doing exactly what the people in the video did - and Americans are still dying of cancer at more or less exactly the same rate. My opponent did not respond to this.

Confirmation BiasFor the Virginia and Madrid studies, my opponent says that what is tested does not make something confirmation-biased. This is true. I claim, however, that the method used was biased. If you look for evidence of something, then you are biased towards that explanation. Most scientists use a method called blinding to avoid this, meaning that the experimenters don't know what they're looking for or what they're injecting the mice with. However, no controls were used to ensure the researcher's inherent bias did not affect the outcome.My opponent also makes a second claim, that I cannot read minds and therefore don't know if the researchers were biased. This is where it is true that what is tested makes someone biased. If I have no claim to prove about Pepsi, I won't experiment on Pepsi. If I do, that makes me biased.For the California study, I did not claim confirmation bias. I claimed that the study tested the effect of cannabidol on THC, found there was an effect, and concluded that cannabidol helps cure cancer. This can only be true if THC cures cancer. Therefore the study presupposed that THC cures cancer. This is no non-sequiter!My opponent notes that both substances were also tested in the California study. The testing that was done was for autophagy - the process that was isolated in the Madrid study. If looking for signs of autophagy was fallacious in the Madrid study, why would it be non-fallacious just because the experiment was carried out in another university?

Use of MiceOn the Virginia study, my opponent claims the chances are human cells were used. Again, the lack of supplementary materials makes this point moot. At best, neither of us has any idea what happened at this study because all we have is sensational newspaper reports and a short abstract. At worst, you'd think that a crucial detail like that would be in the abstract, wouldn't you? While the Virginia researchers were very careful to note what type of cancer they investigated, they omitted to mention if it was human or mouse. This is remarkably suspicious. I say we should approach such inconclusive and probably irrelevant research with a great deal of skepticism.On the california study, my opponent says that humans were used. Technically this is not true. Human cells were used, but only in the test tube, under very controlled conditions of temperature and environment.

Sample SizeMy opponent states the number of studies and similar results is a surrogate for sample size. So what studies have there been? My opponent only cited one study that was taken under controlled conditions which involved humans (sum total of two), one more that involved mice (about a dozen per study, sample size of about 25-30), and one more that involved cells cultured in the lab (ok, let's be generous and say 50). Any statistician would laugh at that sum to try to prove anything scientifically.Assuming a 3% margin of error and 99% confidence level (very reasonable assumptions), the minimum sample size you would need is (rounded) 1849 people.

Cancer really sucks, and I'm all for investigating alternatives. However, the research on THC is presently still very sketchy. A vote for con is a vote for continuing that research, not jumping to conclusions.

So you can post in 3 days? I was planning to post tomorrow. You have 3 days from when I post, meaning your deadline will be 4 days from today, a day after you get back from your trip. If you want, though, I will keep my post until the very last minute, 2 (and a third) days from now. That will give you an extra day to consider your response. Sound good?

Reasons for voting decision: Pro dropped A LOT of arguments, in his last round. This makes him appear to dodge the debate, rather than tackle it head on. One thing that he could have done was say bias =/= false, and so the results cannot be dismissed on that nature alone.

Reasons for voting decision: "Con has not substantiated his claim that the Virginia study is an example of confirmation bias." - that is why you have to use double blind. Nice rebuttal by Larz, 3:2 Con.

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